Blind Spot and the "Filling-in" phenomenon.

Did you know that your eyes have blind spots (and not just at the back of your head)?
Each of your eyes contains an area that has no photoreceptors because it is occupied by
the optic nerve. You may not have noticed these areas because they are on opposite sides
of your visual field. However, this exercise is designed to isolate your blind spot and
you will be amazed at the results.

Instructions: Close your left eye and fixate your right
eye on the cross in the first diagram. If your eye is about 12 inches (30 cm) away from
the monitor, you should notice that the round dot disappears. This distance may vary
according to the screen resolution you have set.

You may be surprised to see that the dot is replaced, not by a black
region, but rather blank white space. The brain simply "fills in" the most
probable stimulus (in this case, a uniform white area) where there is none.

The following examples demonstrate the "filling-in" phenomenon
in greater detail. Apply the same instructions as given above and you should notice the
red markings each time are replaced by the most probable pattern that your brain is able
to perceive.